Remediating the Largest Superfund Site in the Country – the Main San Gabriel Basin

The San Gabriel Basin is the largest USEPA groundwater Superfund site in the country. With the groundwater basin providing 90% of the drinking water supply to 1.4 million residents, and an extended drought limiting basin supply, remediating the five separate areas each with distinct contaminant signatures is top priority for the region. The ongoing multi-decade effort required an innovative approach to remediation that included the first perchlorate treatment facility in the nation to be permitted for drinking water supply. Additionally, these efforts required water agencies to be the first to navigate a strict, newly formed California policy for permitting extremely impaired sources entitled Policy 97-005. Several of the large scale 97-005 cleanups projects required the use of the multiple technologies for treatment of contaminants including VOCs, perchlorate, NDMA, 1,4-dioxane, CrVI and 1,2,3 TCP.